In gas turbine engines, oil supply systems typically circulate the used oil mixture from the various enclosures requiring lubrication, such as the main bearing cavities, to the accessory gearbox cavity to reach the oil tank and/or directly to the oil tank, where the used oil mixture rests for a period of time in order to be sufficiently deaerated for recirculation. The deaerated oil is then typically circulated from the oil tank directly back to the enclosures, while the air separated from the used oil mixture circulates from the tank to the gearbox cavity, where it is vented to the atmosphere after having passing through a centrifugal breather to extract residual oil contained therein. The dwell time of the oil in the tank increases the quantity of oil necessary in the system, and as such the size of the tank required to contain it. This increases the overall weight of the engine, which is undesirable.
Known oil supply systems which are suitable for maneuvers at extreme attitudes, including negative gravity (“G”) forces, comprise systems having two alternative oil circulation paths, combined with a valve or similar element which allows for the selection of one of the two circulation paths depending on the gravity experienced by the system. The addition of an alternate circulation path for extreme attitudes generally increases the complexity and weight of the system, and the valve or similar element may be prone to failure.
Accordingly, improvements are desirable.